1. Field of the Invention
This invention relates to a flash photography system and more particularly to a flash photography system of the type which determines a diaphragm aperture value corresponding to the distance to the object to be photographed by pre-flashing a light before a main flashing action is performed at the determined aperture value.
2. Description of the Prior Art
Photographic flash devices have been known of the type in which a pre-flashing action is performed to detect an object distance and to determine a diaphragm aperture value according to the detected distance before flash photography is carried out at the determined aperture value. In flash devices of this type, the aperture value is determined according to the distance to the object and flash photography is carried out at the aperture value so that the flash photography is always adequate. However, in photographing with a flash device of this type, if the object is located at a distance greater than that which can be covered by the light emitting capacity of the flash device, it is hardly possible to obtain an adequate exposure even if the aperture value is predetermined by the pre-flashing action.
When the aperture value determined by pre-flashing is smaller than the full-open F-number of the lens in use, the diaphragm cannot be set at the aperture value determined by pre-flashing (a designated aperture value). Then, it is impossible to have proper exposure.
Furthermore, when the object to be photographed is located at a very short distance from the camera, flash photography results in overexposure even if it is carried out at an aperture value determined in accordance with the distance determined by pre-flashing.
The flash device of the above type has thus been incapable of ensuring proper exposure where the object to be photographed is located beyond a range of distances detectable by pre-flashing and where the object is located at a very short distance. It is, therefore, desirable for a flash device of this type to ensure a proper exposure even for an object located at a great distance. This is possible by having the flash device perform the pre-flashing action for determining an aperture value after the main capacitor thereof has been amply charged to impart a sufficient flashing power to the flash device. This arrangement, however, necessitates inhibiting flash photography until the main capacitor has been sufficiently charged. Then, with the flash device arranged in this manner, the photographer tends to miss photographing opportunities. Meanwhile, if an object is located at a relatively short distance, the main capacitor does not have to be fully charged to obtain a proper exposure. In spite of this, inhibition of flash photography until the main capacitor is sufficiently charged for an object located at a greater distance deprives the photographer of an opportunity for photographing a closer object.
It is an object of the present invention to provide a flash photography system for a photographic camera which obliterates the above stated shortcomings of the prior art either by inhibiting a flashing action or by shifting the control mode of the camera to a daylight photography mode when an object to be photographed is located beyond an adequately operable distance.
It is another object of the invention to provide a flash photography system which obliterates the above shortcomings of the prior art arrangement either by inhibiting a flashing action or by shifting the control mode of the camera from flash photography to daylight photography when the object to be photographed is located at an extremely short distance.
It is a further object of the invention to provide a flash photography system for a camera which either inhibits a flashing action or shifts the control mode of the camera from a flash photography mode to a daylight photography mode when an aperture value is determined by the distance to an object to be photographed and is smaller than the full-open F-number of the lens of the camera.
It is still a further object of the invention to provide a flash photography system for a camera wherein the distance to an object is detected by pre-flashing, etc., when a main capacitor is charged to a given level before the capacitor is fully charged; then when the distance is within an adequately operable range, flash photography is performed at a diaphragm aperture value which is determined on the basis of the detected distance; or the main capacitor is further charged for an increased flashing power when the distance detected is outside of the adequately operable range. Then, in the latter case, the distance to the object is again detected by a second pre-flashing action and flash photography is carried out at an aperture value determined on the basis of the distance detected by the second pre-flashing action, so that flash photography can be carried out at a desired shutter chance for an object located at a relatively short distance in a shorter charging time, without waiting until the main capacitor is fully charged for objects located at greater distances.
These and further objects and features of the invention will become apparent from the following detailed description of preferred embodiments thereof taken in conjunction with the accompanying drawings.